BIODEGRADABLE MULTI-LAYER FILM

Abstract

A multi-layer polymer film comprising at least one middle layer A, the polymeric constituents of which are soluble in aqueous solution, and in each case at least one substantially water-impermeable covering layer B, C arranged above and below the at least one middle layer A, wherein the layers A, B and C independently of each other in each case comprise at least one thermoplastic polymer and at least one of the covering layers B and C comprises at least one polyhydroxyalkanoate is presented and described. Processes for the production of the multi-layer polymer film according to the invention and its use for the production of molded parts, films or bags are furthermore presented and described.

Claims

1. A multi-layer polymer film comprising at least one middle layer A, the polymeric constituents of which are soluble in aqueous solution, and in each case at least one substantially water-impermeable covering layer B, C arranged above and below the at least one middle layer A, wherein the layers A, B and C independently of each other in each case comprise at least one thermoplastic polymer and at least one of the covering layers B and C comprises at least one polyhydroxyalkanoate.

2. The polymer film according to in claim 1, wherein the polyhydroxyalkanoate is contained in at least one of the covering layers B and C in an amount of at least 10 wt. %, in particular at least 15 wt. % or 20 wt. %, based on the total weight of the particular covering layer.

3. The polymer film according to claim 1, wherein the in each case at least one thermoplastic polymer of the covering layers B and C can be decomposed by hydrolysis.

4. The polymer film according to claim 1, wherein the in each case at least one thermoplastic polymer of the covering layers B and C independently of each other is selected from the group consisting of thermoplastic starch, starch-containing thermoplastics, polyvinyl alcohol, thermoplastic polyvinyl alcohol, polyvinyl acetate, poly(3-hydroxybutanoate), poly(3-hydroxyvalerate), poly(3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), polylactic acid, polycaprolactone, polybutylene succinate, poly(butylene adipate-co-succinate), aromatic-aliphatic copolyester, poly(butylene adipate-co-terephthalate), poly(butylene seb acate-co-terephthalate) and mixtures thereof.

5. The polymer film according to claim 1, wherein the polyhydroxyalkanoate in at least one of the covering layers B and C is selected from the group consisting of poly(3-hydroxybutanoate), poly(3-hydroxyvalerate), poly(3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and mixtures thereof.

6. The polymer film according to claim 1, wherein polyhydroxyalkanoate in at least one of the covering layers B and C has been produced by microorganisms in a fermentation process and/or by chemical synthesis.

7. The polymer film according to claim 1, wherein the covering layers B and C in each case comprise at least one polyhydroxyalkanoate.

8. The polymer film according to claim 1, wherein the at least one thermoplastic polymer of the covering layers B and/or C is the polyhydroxyalkanoate.

9. The polymer film according to claim 1, wherein the covering layers B and/or C, in accordance with ASTM D6866, in each case comprise at least 40%, in particular at least 45% or 50% of biobased carbon, based on the total amount of carbon of the particular covering layers.

10. The polymer film according to claim 1, wherein the covering layers B and/or C, in accordance with ISO 15985 and/or in accordance with ISO 14855, are biodegradable to the extent of in each case at least 40%, in particular at least 45% or at least 50%, at least 60%, at least 80%, at least 90% or at least 95%.

11. The polymer film according to claim 1, wherein the middle layer A, in accordance with ISO 15985 and/or in accordance with ISO 14855, is biodegradable to the extent of at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90% or at least 95%.

12. The polymer film according to claim 1, wherein the at least one thermoplastic polymer of the middle layer A is selected from the group consisting of thermoplastic starch, starch-containing thermoplastics, polyvinyl alcohol, thermoplastic polyvinyl alcohol, polyvinyl acetate, polyethylene glycol, cellulose acetate, ethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, poly(vinylpyrrolidone), poly(3-hydroxybutanoate), poly(3-hydroxyvalerate), poly(3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), polylactic acid, polycaprolactone, polybutylene succinate, poly(butylene adipate-co-succinate), aromatic-aliphatic copolyester, poly(butylene adipate-co-terephthalate), poly(butylene seb acate-co-terephthalate) and mixtures thereof.

13. The polymer film according to claim 1, wherein the polymer film has in the dry state an elongation at break in the extrusion direction (MD) in accordance with EN ISO 527 of 100% or more, in particular of 150% or more, 180% or more, 200% or more, 220% or more or 250% or more.

14. The polymer film according to claim 1, wherein the polymer film has in the dry state an elongation at break transversely to the extrusion direction (TD) in accordance with EN ISO 527 of 100% or more, in particular of 150% or more, 180% or more, 200% or more, 220% or more or 250% or more.

15. The polymer film according to claim 1, wherein the polymer film has in the dry state a specific dart drop value in accordance with ASTM D1709 of at least 5 ghim.

16. The polymer film according to claim 1, wherein the covering layers B and/or C independently of each other disintegrate in aqueous solution within at most 14 days, in particular within at most 10 days or at most 7 days, into parts having a surface area of in each case at most 60% of the total surface area of the Currently Amended polymer film.

17. The polymer film according to claim 1, wherein the covering layers B and/or C independently of each other disintegrate in aqueous solution within at most 14 days, in particular within at most 10 days or at most 7 days, into parts having a surface area of in each case at most 100 cm.sup.2.

18. The polymer film according to claim 1, wherein the polymer film has a total thickness of from 10 m to 80 km, in particular from 20 pm to 60 km, 20 km to 40 km, 20 km to 35 km or 25 to 35 km.

19. The polymer film according to claim 1, wherein the middle layer A of the polymer film makes up 30% to 90%, in particular 40% to 85%, 40% to 80% or 60% to 80% of the total thickness of the polymer film.

20. The polymer film according to claim 1, wherein the covering layers B and C of the polymer film together make up 10% to 70%, in particular 15% to 60%, 20% to 60% or 20% to 40% of the total thickness of the polymer film.

21. The polymer film according to claim 1, wherein the covering layers B and/or C independently of each other have places with a lower resistance to mechanical influences and/or to aqueous solutions.

22. The polymer film according to claim 1, wherein the covering layers B and/or C independently of each other comprise a water-soluble polymer.

23. The polymer film according to claim 1, wherein the surfaces of the covering layers B and/or C independently of each other have a corrugated surface.

24. The polymer film according to claim 1, wherein the covering layers B and/or C have in the dry state in each case a specific dart drop value of at least 5 ghtm in accordance with ASTM D1709.

25. The polymer film according to claim 1, wherein the covering layers B and/or C independently of each other have a tensile strength in the extrusion direction (MD) of at least 10 MPa, in particular at least 15 MPa or at least 20 MPa, in accordance with EN ISO 527.

26. The polymer film according to claim 1, wherein the covering layers B and/or C independently of each other have a tensile strength transversely to the extrusion direction (TD) of at least 10 MPa, in particular at least 15 MPa or at least 20 MPa, in accordance with EN ISO 527.

27. The polymer film according to claim 1, wherein the covering layers B and/or C independently of each other have an elongation at break in the extrusion direction (MD) of at least 100%, in particular at least 150%, at least 180% or at least 200%, in accordance with EN ISO 527.

28. The polymer film according to claim 1, wherein the covering layers B and/or C independently of each other have an elongation at break transversely to the extrusion direction (TD) of at least 100%, in particular at least 150%, at least 180% or at least 200%, in accordance with EN ISO 527.

29. The polymer film according to claim 1, wherein the middle layer A has a tensile strength in the extrusion direction (MD) of at least 10 MPa, in particular at least 15 MPa, in accordance with EN ISO 527.

30. The polymer film according to claim 1, wherein the middle layer A has a tensile strength transversely to the extrusion direction (TD) of at least 10 MPa, in particular at least 15 MPa, in accordance with EN ISO 527.

31. The polymer film according to claim 1, wherein the middle layer A has an elongation at break in the extrusion direction (MD) of at least 100%, in particular at least 150%, or at least 200%, in accordance with EN ISO 527.

32. The polymer film according to claim 1, wherein the middle layer A has an elongation at break transversely to the extrusion direction (TD) of at least 100%, in particular at least 150%, or at least 200%, in accordance with EN ISO 527.

33. The polymer film according to claim 1, wherein the covering layers B and C are identical.

34. A multi-layer polymer film comprising at least one middle layer A, the polymeric constituents of which are soluble in aqueous solution, and in each case at least one substantially water-impermeable covering layer B, C arranged above and below the at least one middle layer A, wherein the layers A, B and C independently of each other in each case comprise at least one thermoplastic polymer, characterized in that the layer A has a tensile strength in accordance with EN ISO 527 of at least 15 MPa and the layers B and C in each case have a tensile strength in accordance with EN ISO 527 of at least 20 MPa.

35. (canceled)

36. A process for the production of a multi-layer polymer film at least comprising a middle layer A, the polymeric constituents of which dissolve in aqueous solution, and in each case at least one substantially water-impermeable covering layer B, C arranged above and below the middle layer, wherein the layers A, B and C independently of each other in each case comprise at least one thermoplastic polymer and at least one of the covering layers B and C comprises at least one polyhydroxyalkanoate, comprising: a. provision of a polymer composition of the first covering layer which comprises at least one polyhydroxyalkanoate, b. forming of the first covering layer, c. provision of at least one thermoplastic polymer of the middle layer, d. forming of a middle layer, e. provision of a polymer composition of the second covering layer, and f. forming of the second covering layer.

37. The process according to in claim 36, wherein steps b., d. and f. are carried out simultaneously.

38. The process according to claim 36, wherein the process includes a coextrusion step.

39. The process according to claim 36, wherein the process comprises a laminating step.

40. The process according to claim 36, wherein at least one polyhydroxyalkanoate is added to the polymer composition in step e.

41. The process according to claim 36, further comprising forming the multi-layer polymer film into molded parts, films or bags.

42. A molded part, film or bag produced from a multi-layer polymer film according to claim 1.

Description

EXAMPLE 1 (COMPARATIVE EXAMPLE)

[0125] Using a twin-screw extruder (co-rotating) of the Werner & Pfleiderer (COPERION) ZSK 70 type, screw diameter 70 mm, L/D=36, the following polymer blend A was compounded (metered contents in percent by weight):

TABLE-US-00001 TABLE 1 Recipe A A PBAT 57.4 Starch 42.6

[0126] The following compounding parameters were maintained here:

TABLE-US-00002 TABLE 2 Temperature profile ZSK 70 Zone Zone Zone Zone Zone Zone Zone Zone Zone Zone Zone 1 2 3 4 5 6 7 8 9 10 11 Die 25 C. 190 C. 190 C. 190 C. 170 C. 170 C. 170 C. 170 C. 155 C. 100 C. 150 C. 140 C.

[0127] Melt temperature at the die opening: 163 C.

[0128] Speed of rotation: 205 min.sup.1

[0129] Throughput: 400 kg/h

[0130] Degasification: active (vacuum, zone 9)

[0131] Water content: less than 1 wt. %

[0132] (measured after exit from the extruder)

[0133] Using a single-screw extruder of the COLLIN 30 (DR. COLLIN) type, screw diameter 30 mm, L/D=33, thermoplastic starch (TPS) with the following recipe was furthermore compounded (metered contents in percent by weight):

TABLE-US-00003 TABLE 3 TPS recipe TPS Glycerin 20 Sorbitol 10 Starch 70

[0134] Granules A were then melted with a single-screw extruder of the COLLIN 30 (DR. COLLIN) type, screw diameter 30 mm, L/D=33 and processed together with the thermoplastic starch TPS, which was likewise melted in a single-screw extruder of the COLLIN 30 (DR. COLLIN) type, screw diameter 30 mm, L/D=33, in a coextrusion step to give a three-layer film, wherein the middle layer comprised TPS and the covering layers comprised composition A. The mechanical properties of the three-layer film as well as the decomposability of the covering layers into smaller parts and the solubility of the middle layer in water were investigated.

[0135] For the investigation of the stability of the three-layer film in water, specimens of the film were clamped in slide frames and laid in natural sea water. The film was furthermore exposed to mechanical stress. The decomposition of the film was evaluated visually.

[0136] The results of this investigation are summarized in the following table.

TABLE-US-00004 TABLE 4 Mechanical properties of the three-layer film and decomposability/solubility in water Thickness Specific Tensile Elongation covering Thickness dart drop strength at break layers middle [g/m] [MPa] [%] (each) layer ASTM D EN ISO 527 EN ISO 527 Decomposability Solubility [m] [m] 1709 MD TD MD TD covering layers middle layer 10 10 8 10.7 7.6 475 230 No Middle layer decomposition intact after after 14 days 14 days due to intact covering layers

[0137] As can be seen from the table, the resulting film on the one hand has a tensile strength which are inadequate for the requirements of a bag. Furthermore, after 14 days no decomposition of the covering layers was to be seen, for which reason the film was still intact even after 14 days.

EXAMPLE 2

[0138] Using a twin-screw extruder (co-rotating) of the Werner & Pfleiderer (COPERION) ZSK 40 type, screw diameter 40 mm, L/D=42, the following recipe B was compounded (metered contents in percent by weight):

TABLE-US-00005 TABLE 5 Recipe B PBAT 44.6 PHBH 19.8 Starch 20.5 PVOH 10 PLA 5.1

[0139] The following compounding parameters were maintained here:

TABLE-US-00006 TABLE 6 Temperature profile ZSK 40 Zone Zone Zone Zone Zone Zone Zone Zone 1 2 3 4 5 6 7 8 Die 25 C. 150 C. 150 C. 140 C. 130 C. 130 C. 130 C. 130 C. 130 C.

[0140] Melt temperature at the die opening: 133 C.

[0141] Speed of rotation: 140 min.sup.1

[0142] Throughput: 40 kg/h

[0143] Degasification: active (vacuum, zone 7)

[0144] Water content: less than 1 wt. %

[0145] (measured after exit from the extruder)

[0146] Granules B were then melted with a single-screw extruder of the COLLIN 30 (DR. COLLIN) type, screw diameter 30 mm, L/D=33 and processed together with PVOH, which was likewise melted in a single-screw extruder of the COLLIN 30 (DR. COLLIN) type, screw diameter 30 mm, L/D=33, in a coextrusion step to give a three-layer film, wherein the middle layer comprised PVOH and the covering layers comprised composition B. The mechanical properties of the three-layer film as well as the decomposability of the covering layers into smaller parts and the solubility of the middle layer in water were investigated.

[0147] For the investigation of the stability of the three-layer film in water, specimens of the film were clamped in slide frames and laid in natural sea water. Furthermore, the film was exposed to mechanical stress. The decomposition of the film was evaluated visually.

[0148] The results of this investigation are summarized in the following table.

TABLE-US-00007 TABLE 7 Mechanical properties of the three-layer film and decomposability/solubility in water Thickness Specific Tensile Elongation covering Thickness dart drop strength at break layers middle [g/m] [MPa] [%] (each) layer ASTM D EN ISO 527 EN ISO 527 Decomposability Solubility [m] [m] 1709 MD TD MD TD covering layers middle layer 10 10 25.4 37.0 40.3 281 234 Smaller parts Completely after 7 days dissolved after 7 days

[0149] The table shows for this film significantly increased values for the tensile strength and good values for the elongation at break, which render it suitable, for example, for a bag. It was furthermore observed that after a few days both covering layers started to disintegrate into smaller parts, which exposed the middle layer, the polymeric constituents of which dissolved in aqueous solution.

EXAMPLES 3 to 15

[0150] Using a 5-layer blown film line of the Biotem 10 15 (Dr. Collin) type with screw diameters of 20 mm, L/D=25, for the outer four layers and a screw diameter of 25 mm, L/D=25, for the inner layer, multi-layer films were produced. The following recipes were compounded in the extruders here for the covering layers (metered amounts in percent by weight):

TABLE-US-00008 TABLE 8 Recipes for the covering layers C D E F G H J PHBH 84 72 63 26 30 58 75 PBAT 16 15 21 41 42 26 10 PBST 13 Starch 15 30 28 15 PLA 1 3 1 PCL 15 K L M N O PHBH 70 30 70 31 95 PBAT 17 42 PBSA 13 Starch 28 PLA 30 69 PCL 5

[0151] For multi-layer films in which recipe L was used for the covering layers TPS (see Example 1) was used for the middle layer. For multi-layer films in which recipes C to K, M to O and pure PHBH were used for the covering layers PVOH was used for the middle layer. The following combinations thus resulted for the multi-layer films:

TABLE-US-00009 TABLE 9 Combinations of the recipes of the covering layers with the various middle layers Multi-layer film no. Covering layers Middle layer I PHBH PVOH II Recipe C PVOH III Recipe D PVOH IV Recipe E PVOH V Recipe F PVOH VI Recipe G PVOH VII Recipe H PVOH VIII Recipe J PVOH IX Recipe K PVOH X Recipe L TPS XI Recipe M PVOH XII Recipe N PVOH XIII Recipe O PVOH

[0152] The following processing parameters were maintained:

TABLE-US-00010 TABLE 10 Temperature profile Biotem 1015 Covering Zone Zone Zone Zone Flange layer Extruder 1 2 3 4 1 Die PHBH, covering 25 C. 160 C. 165 C. 165 C. 165 C. 170 C. recipes layers C, D, G, middle 25 C. 185 C. 185 C. 185 C. 185 C. 175 C. J, K, O layer Recipes covering 25 C. 180 C. 180 C. 180 C. 180 C. 175 C. E, F, H layers middle 25 C. 185 C. 185 C. 185 C. 185 C. 175 C. layer Recipe L covering 25 C. 160 C. 165 C. 165 C. 165 C. 170 C. layers middle 25 C. 165 C. 165 C. 165 C. 165 C. 165 C. layer Recipes covering 25 C. 180 C. 185 C. 185 C. 185 C. 185 C. M, N layers middle 25 C. 185 C. 185 C. 185 C. 185 C. 175 C. layer

[0153] Speed of rotation: 55-90 min.sup.1

[0154] Annular die: diameter 60 mm

[0155] Annular gap: 1.20 mm

[0156] Blow-up ratio: approx. 1:3.

[0157] Films having a total thickness of from 20 to 35 m were produced. The multi-layer films had the construction of covering layer-covering layer-middle layer-covering layer-covering layer. The individual layers here had a ratio of covering layer:covering layer:middle layer:covering layer:covering layer of 1:1:2-4:1:1.

[0158] The films were then stored for at least 72 hours, before the mechanical properties were investigated.

TABLE-US-00011 TABLE 11 Mechanical properties of the multi-layer films Tensile strength Elongation at break Specific dart drop [MPa] [%] [g/m] EN ISO 527 EN ISO 527 Film ASTM D 1709 MD TD MD TD I 6 35 37 190 410 II 7 27 25 320 450 III 8 23 24 457 530 IV 8 24 26 418 491 V 11 37 40 281 234 VI 10 28 30 405 436 VII 5 37 28 216 228 VIII 9 22 24 480 562 IX 6 32 31 310 378 X 7 11 10 513 444 XI 5 47 49 209 220 XII 5 52 55 123 147 XIII 7 26 28 280 452

[0159] The table shows that on the basis of their mechanical properties films I to IX and XI to XIII are suitable in particular for plastic carrier bags. It was likewise observed that films I to XIII, when clamped in slide frames, laid in natural sea water and exposed to mechanical stress, disintegrated into smaller parts after several days in water. The middle layer dissolved here and the covering layers disintegrated into smaller parts.